With the increasing demand and higher price of fossil fuels, in addition to global warming concerns from carbon dioxide emissions, energy storage systems such as batteries and capacitors with substantially higher energy and power densities are urgently needed in transportation and other applications. Lithium ion batteries have been identified as a critical enabling technology for development of advanced, fuel-efficient vehicles, especially for plug-in hybrid electrical vehicles (PHEVs). However, there is a need to have lithium ion batteries with a higher energy density, longer cycle life and calendar life, higher safety, and lower cost than the currently known lithium ion batteries.
One way to significantly increase the energy density of a lithium ion battery is to use electrode materials with high capacity stored reversibly per unit weight, particularly for the anode material. Commercially available lithium ion batteries mainly use carbonaceous materials, especially graphite, as the anode material. Graphite has a theoretical specific capacity of 372 mAh/g and good cell performance. There is an urgent need to replace graphite with an anode having superior capacity and an electrochemical potential that is within a few hundred millivolts above that of metallic lithium to minimize lithium plating on the anode.